DNA markers linked to yield, yield components, and morphological traits in autotetraploid lucerne (Medicago sativa L.)

We have mapped and identified DNA markers linked to morphology, yield, and yield components of lucerne, using a backcross population derived from winter-active parents. The high-yielding and recurrent parent, D, produced individual markers that accounted for up to 18% of total yield over 6 harvests, at Gatton, south-eastern Queensland. The same marker, AC/TT8, was consistently identified at each individual harvest, and in individual harvests accounted for up to 26% of the phenotypic variation for yield. This marker was located in linkage group 2 of the D map, and several other markers positively associated with yield were consistently identified in this linkage group. Similarly, markers negatively associated with yield were consistently identified in the W116 map, W116 being the low-yielding parent. Highly significant positive correlations were observed between total yield and yield for harvests 1-6, and between total yield and stem length, tiller number, leaf yield/plant, leaf yield/5 stems, stem yield/plant, and stem yield/5 stems. Highly significant QTL were located for all these characters as well as for leaf shape and pubescence.

DNA amplification fingerprinting analysis of genetic variation within Fusarium oxysporum f.sp zingiberi

Genetic variation among 29 isolates of Fusarium oxysporum f.sp. zingiberi (Foz) collected from diseased ginger rhizome in production regions throughout Queensland was analysed using DNA amplification fingerprinting (DAF). Eight isolates of other Fusarium species and/or formae speciales were included for comparative analysis. Within the Foz isolates, three haplotypes were identified based on 17 polymorphic bands generated with five primers. Two groups showed very little genetic variation (98.6% similarity), whereas the third single isolate was quite distinct in terms of its molecular profile (77.2% similarity). Genetic similarity among the Fusarium solani, F. oxysporum f.sp. lycopersici and F. oxysporum f.sp. cubense races 1, 3 and 4 isolates compared well with the published literature.

Cyclic Peptide Disulfides - Solution And Solid-State Conformation Of Boc-Cys-Pro-Aib-Cys-S-S-Bridge-Nhme,A Disulfide-Bridged Peptide Helix

The solution and solid-state conformations of the peptide disulfide Boc-Cys-Pro-Aib-Cys-NHMe have been determined by NMR spectroscopy and X-ray diffraction. The Cys(4) and methylamide NH groups are solvent shielded in CDCI3 and (CD,),SO, suggesting their involvement in intramolecular hydrogen bonding. On the basis of known stereochemical preferences of Pro and Aib residues, a consecutive @-turn structure is favored in solution. X-ray diffraction analysis reveals a highly folded 310 helical conformation for the peptide, with the S-S bridge lying approximately parallel to the helix axis, linking residues 1 and 4. The backbone conformational angles are Cys(1) 4 = -121.1', $ = 65.6"; Pro(2) 4 = -58.9', 4 = -34.0'; Aib(3) 4 = -61.8', $ = -17.9'; Cys(4) 4 = -70.5', $ = -18.6'. Two intramolecular hydrogen bonds are observed between Cys(1) CO--HN Cys(4) and Pro(2) CO--HNMe. The disulfide bond has a right-handed chirality, with a dihedral angle (xss) of 82'.

The assessment of TGGE for the detection of interspecific and intergeneric DNA-marker polymorphism within Solanaceae

RFLP markers are currently the most appropriate marker system for the identification of uncharacterised polymorphism at the interspecific and intergeneric level. Given the benefits of a PCR-based marker system and the availability of sequence information for many Solanaceous cDNA clones, it is now possible to target conserved fragments, for primer development, that flank sequences possessing interspecific polymorphism. The potential outcome is the development of a suite of markers that amplify widely in Solanaceae. Temperature gradient gel electrophoresis (TGGE) is a relatively inexpensive gel-based system that is suitable for the detection of most single-base changes. TGGE can be used to screen for both known and unknown polymorphisms, and has been assessed here, for the development of PCR-based markers that are useful for the detection of interspecific variation within Solanaceae. Fifteen markers are presented where differences between Lycopersicon esculentum and L. pennellii have been detected by TGGE. The markers were assessed on a wider selection of plant species and found to be potentially useful for the identification of interspecific and intergeneric polymorphism in Solanaceous plants.

An identification tool for the Australian weedy Sporobolus species based on random amplified polymorphic DNA (RAPD) profiles

Based on morphological features alone, there is considerable difficulty in identifying the 5 most economically damaging weed species of Sporobolus [viz. S. pyramidalis P. Beauv., S. natalensis (Steud.) Dur and Schinz, S. fertilis (Steud.) Clayton, S. africanus (Poir.) Robyns and Tourney, and S. jacquemontii Kunth.] found in Australia. A polymerase chain reaction (PCR)-based random amplified polymorphic DNA (RAPD) technique was used to create a series of genetic markers that could positively identify the 5 major weeds from the other less damaging weedy and native Sporobolus species. In the initial RAPD profiling experiment, using arbitrarily selected primers and involving 12 species of Sporobolus, 12 genetic markers were found that, when used in combination, could consistently identify the 5 weedy species from all others. Of these 12 markers, the most diagnostic were UBC51490 for S. pyramidalis and S. natalensis; UBC43310.2000.2100 for S. fertilis and S. africanus; and ORA20850 and UBC43470 for S. jacquemontii. Species-specific markers could be found only for S. jacquemontii. In an effort to understand why there was difficulty in obtaining species-specific markers for some of the weedy species, a RAPD data matrix was created using 40 RAPD products. These 40 products amplified by 6 random primers from 45 individuals belonging to 12 species, were then subjected to numerical taxonomy and multivariate system (NTSYS pc version 1.70) analysis. The RAPD similarity matrix generated from the analysis indicated that S. pyramidalis was genetically more similar to S. natalensis than to other species of the 'S. indicus complex'. Similarly, S. jacquemontii was more similar to S. pyramidalis, and S. fertilis was more similar to S. africanus than to other species of the complex. Sporobolus pyramidalis, S. jacquemontii, S. africanus, and S. creber exhibited a low within-species genetic diversity, whereas high genetic diversity was observed within S. natalensis, S. fertilis, S. sessilis, S. elongates, and S. laxus. Cluster analysis placed all of the introduced species (major and minor weedy species) into one major cluster, with S. pyramidalis and S. natalensis in one distinct subcluster and S. fertilis and S. africanus in another. The native species formed separate clusters in the phenograms. The close genetic similarity of S. pyramidalis to S. natalensis, and S. fertilis to S. africanus may explain the difficulty in obtaining RAPD species-specific markers. The importance of these results will be within the Australian dairy and beef industries and will aid in the development of integrated management strategy for these weeds.

Self-Organization of n-Alkane Chains in Water: Length Dependent Crossover from Helix and Toroid to Molten Globule

We demonstrate a chain length dependent crossover in the structural properties of linear hydrocarbon (n-alkane) chains using detailed atomistic simulations in explicit water. We identify a number of exotic structures of the polymer chain through energy minimization of representative snapshots collected from molecular dynamics trajectory. While the collapsed state is ring-like (circular) for small chains (CnH2n+2; n <= 20) and spherical for very long ones (n = 100), we find the emergence of ordered helical structures at intermediate lengths (n similar to 40). We find different types of disordered helices and toroid-like structures at n = 60. We also report a sharp transition in the stability of the collapsed state as a function of the chain length through relevant free energy calculations. While the collapsed state is only marginally metastable for C20H42, a clear bistable free energy surface emerges only when the chain is about 30 monomers long. For n = 30, the polymer exhibits an intermittent oscillation between the collapsed and the coil structures, characteristic of two stable states separated by a small barrier.

Double-authentication-preventing signatures

Digital signatures are often used by trusted authorities to make unique bindings between a subject and a digital object; for example, certificate authorities certify a public key belongs to a domain name, and time-stamping authorities certify that a certain piece of information existed at a certain time. Traditional digital signature schemes however impose no uniqueness conditions, so a trusted authority could make multiple certifications for the same subject but different objects, be it intentionally, by accident, or following a (legal or illegal) coercion. We propose the notion of a double-authentication-preventing signature, in which a value to be signed is split into two parts: a subject and a message. If a signer ever signs two different messages for the same subject, enough information is revealed to allow anyone to compute valid signatures on behalf of the signer. This double-signature forgeability property discourages signers from misbehaving—a form of self-enforcement—and would give binding authorities like CAs some cryptographic arguments to resist legal coercion. We give a generic construction using a new type of trapdoor functions with extractability properties, which we show can be instantiated using the group of sign-agnostic quadratic residues modulo a Blum integer; we show an additional application of these new extractable trapdoor functions to standard digital signatures.

On prequantization to reduce errors in double phase holograms

Prequantization has been forwarded as a means to improve the performance of double phase holograms (DPHs). We show here that any improvement (even under the best of conditions) is not large enough to help the DPH to compete favourably with other holograms.

Mitochondrial DNA supports the identification of two endangered river sharks (Glyphis glyphis and Glyphis garricki) across northern Australia

The river sharks (genus Glyphis) are a small group of poorly known sharks occurring in tropical rivers and estuarine waters across northern Australia, south-east Asia and the subcontinent. The taxonomy of the genus has long been unclear due to very few individuals having been caught and examined, resulting in a paucity of data regarding their distribution, biology and ecology. Only recently has attention focussed on the two Australian species, G. glyphis and G. garricki. This study is a result of a rare opportunity to collate the few samples that have been collected from these species and the bull shark Carcharhinus leucas, which shares an overlapping range. These samples were analysed using the DNA barcoding approach (cox1 mitochondrial gene), compared with six other species of carcharhinids and evaluated in light of the current taxonomic classification. Nine species-specific nucleotide differences were found between G. glyphis and G. garricki and no intra-specific variation provides strong support for the separation into distinct species. Significant differences were also observed at the inter-generic level, with Glyphis forming a distinct clade from Carcharhinus. This study provides the basis for future molecular studies required to better address conservation issues confronting G. glyphis and G. garricki in Australia.

Topochemical dimerization of non-parallel double bonds: 7-methoxycoumarin

X-ray crystal structure analysis of 7-methoxycoumarin reveals that the reactive double bonds are rotated by about 65° with respect to each other, the centre-to-centre distance between the double bonds being 3.83 Å. In spite of this unfavourable arrangement, photodimerization occurs in the crystalline state yielding the syn-head-tail dimer as the only product. Lattice energy calculations on ground-state molecules in crystals throw light on the mechanism of the reaction.